Most sexual assaults are never reported to authorities - and that's why it's so important to Benton County officials that those victims of sexual assaults who do step forward are treated with care and compassion each step of the way.

Corvallis police and the Benton County Sheriff's Office investigated 22 reports of sexual assault between July 2005 and June 2006. Oregon State Police on the Oregon State University campus investigated three cases during the same 12-month period.

But sexual assault is widely acknowledged to be an underreported crime. The federal Bureau of Justice Statistics reports that in the 1990s, there was an annual average of 366,460 incidents of sexual assault of people over the age of 12. As many as 63 percent of completed rapes, 65 percent of attempted rapes and 74 percent of attempted sexual assaults are not reported to law enforcement, the bureau says. So local law enforcement numbers are likely correspondingly low.

The reasons for not reporting are varied. According to the bureau's study, the most common reasons include:

• Some victims believe that sexual assault is a "personal matter."

• Victims fear reprisal.

• Victims believe the police are biased against them.

The closer the relationship of the victim to the attacker - if the two are married, for instance - the less likely the victim is to report to law enforcement.

All of that helps underscore the importance of making sure that victims who do report the crime get treated well by the system. In addition, the clock is ticking for authorities to gather the physical evidence they need to build their case.

"We have 84 hours to collect evidence from the time of the assault, to get DNA evidence," said Cindy Roler, a sexual assault nurse examiner at Good Samaritan Medical Center.

Evidence must be properly collected and the chain of custody maintained for any future legal proceedings. The state provides funds for collecting and maintaining the evidence, so cost need not be a factor. But if the victim is traumatized and unwilling or unable to talk to law enforcement, those hours can slip by.

"It's a very stressful time for people," Roler said.

The Oregon State Police office on the OSU campus began a new program in January that gives victims more time to make up their minds about pursuing a case legally.

"We'll take the evidence anonymously," said OSP Lt. Phil Zerzan, "if we can reasonably relate (the case) to the university. We'll hold it for six months."

At Good Samaritan, Chris Boos, the manager of the emergency department, said the hospital doesn't have the facilities to maintain evidence anonymously.